HERA - a unique machine to see inside the proton

24 March 1999

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HERA (the Hadron-Electron Ring Accelerator) at the DESY laboratory in Hamburg provides energetic head-on collisions between the most familiar constituents of matter - electrons and protons. To do this requires two particle accelerators in the same tunnel to provide the beams of different particles. This view inside HERA's 6.3 km long tunnel shows how different the two accelerators appear. Nearest to the floor of the tunnel is the electron accelerator, with one of the long dipole electromagnets that steer electrons round the ring-shaped tunnel visible in the foreground. Above this is the 6.3 km long cryostat that contains the magnets of the proton accelerator. These are superconducting magnets, which rely on superconductivity to reach high electric currents and hence high magnetic fields. To work in this way, they are cooled to -269 C by liquid helium which flows through the cryostat structure.

Credit: DESY

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